The use of various compounds as sizing agents for warp yarns to prevent breakage of the yarns during weaving is well known. The sizing agents are placed upon the warp yarns prior to weaving to provide strength and protection to the yarns from abrasion. Traditional sizing agents for spun yarns have generally included film formers such as starch, starch derivatives, polyvinyl alcohol, polyester resins, waxes, acrylic polymers and copolymers (and their salts), wetting agents, antistatic agents, and the like. Current commercial sizes are predominantly based upon starch in combination with one or more of polyvinyl alcohol, polyester resins, acrylic copolymer resins, and waxes.
A good sizing agent is one which will form a film with sufficient strength to provide protection to the yarn being sized but not so strong that the yarn will break before the size film. This is particularly important as yarns are generally sized in a size box, then the water removed on steam cans and the yarns form a sheet. Then this sheet of yarns is run across bust rods to break the sheet back into individual yarns for weaving.
Most previous attempts to utilize polyacrylamide homopolymers as sizing agents have not been successful. For example, U.S. Pat. No. 4,515,855 claims the use of acrylamide copolymers and multipolymers with at least one monomeric compound containing a hydrophobic polymerizable reactive vinyl or vinylidene group but asserts that homopolymers of acrylamide impart only minor protection to fibers during weaving. Example 11 pads a polyacrylamide polymer solution unto single-end 100% untreated yarns. No indication of the type of polyacrylamide polymer nor its molecular weight are provided. Evaluation of the polyacrylamide padded yarns indicate little difference in performance vs. starch alone and substantially inferior performance as compared to the claimed copolymers and multipolymers. U.S. Pat. No. 4,410,588 contains a similar statement on acrylamide homopolymers but also contains no details thereon.
Commonly owned U.S. Patent No 5,397,633 discloses a process of sizing a spun cotton yarn with a solution polyacrylamide polymer. The present invention is an improvement thereover.
Since prior sizing agents have not been completely adequate for use in processing spun yarns, it is an object of the present invention to overcome certain of the deficiencies of the prior sizes, particularly in the processing of spun yarns, e.g. blends of cotton with polyester, acrylic yarns, and blends of wool with other fibers. More particularly, it is an object of the present invention to overcome certain of the deficiencies when such yarns are to be overdyed.
Furthermore, with the increasing levels of both general environmental concern and garment processing in the denim industry, e.g. stone washing, pre-washing, and the like, it is a further object of the present invention to develop a sizing agent which will be less harmful to the environment than conventional size materials, i.e. one which has a reduced biological oxygen demand (BOD) and chemical oxygen demand (COD).
It is also an object to develop a size composition that is sufficiently water soluble that it can be easily and completely washed from a fabric after weaving, thereby (i) preventing dye defects, (ii) preventing microbial growth due to incomplete removal of the size (as often occurs with conventional sizes), and (iii) saving energy.
It is a still further object of the invention to develop an effective non-ionic sizing agent which will permit the utilization of cationic fixing agents such as polyamine and polyamide polymers.
It is still a further object to develop a size that will not produce "crack" or crease marks on fabrics made of spun yarns, especially on yarn-dyed fabric in garment processing.
It is still a further object of the invention to develop a sizing agent which does not become tacky or sticky in the presence of the very high moisture levels commonly present in weaving rooms.
These and still further objects will be apparent from the following detailed description of the invention.